New and general strategies for the enantio- and regiospecific construction of molecules of medicinal interest (antivirals, antibiotics, antitumor agents, etc.) are important to the overall mission of the NIH. The development of new methods for the regio- and enantiospecific synthesis of highly substituted heterocycles (dihydro- and tetrahydropyrans, furans, piperidines and pyrroles) is described. This proposal will emphasize the use in organic synthesis of various substituted heterocycle-metal pi-complexes (eta4-, eta2-, eta3-2H-furan and pyrrole; eta5-, eta3-, eta4-2H-pyran and pyridine) derived from carbohydrate precursors to provide enantiomerically pure derivatives of the above mentioned classes of compounds. Successful achievement of this new strategy would introduce a novel method for the synthesis of important classes of heterocyclic organic compounds with demonstrated biological activity in a wide variety of assays (antiviral, antibiotic, etc.).